An inspection apparatus includes a loader chamber and a prober chamber arranged adjacent to each other. The loader chamber includes a containing unit for containing target objects to be inspected (e.g., semiconductor wafers) in the unit of cassette, a semiconductor wafer transfer mechanism for transferring semiconductor wafers from the cassette one by one, and a sub-chuck for prealigning semiconductor wafers in the course of transfer. The prober chamber includes a movable main chuck for mounting a semiconductor wafer that has been transferred by the wafer transfer mechanism in the loader chamber, the temperature of the main chuck being adjustable, a probe card arranged above the main chuck, and an alignment mechanism for performing alignment of probes of the probe card and electrode pads of each device formed on the semiconductor wafer on the main chuck. After aligning the electrode pads of the semiconductor wafer and the probes through the alignment mechanism, the temperature of the semiconductor wafer is set to a predetermined level through the main chuck so that the electrical characteristics of the target object are inspected at the set temperature.
In case where the electrical characteristics of every device of the semiconductor wafer are inspected, a photographing unit (e.g., CCD camera) in the alignment mechanism is used to photograph an image of a device including electrode pads on the semiconductor wafer as well as an image of needle tips of the probes of the probe card, and the electrode pads and the probes are aligned based on position information thereof. Next, the semiconductor wafer is lifted by a predetermined distance through a mounting table and overdriven to make electrical contact between the electrode pads and the probes to thereby inspect electrical characteristics of the device. However, to keep abreast with the trend of high integration of the device, electrode pads have been made markedly finer and at the same time, the number of pads and the number of probes of the probe card have been markedly increased. Therefore, it becomes difficult for the CCD camera to detect probes during the alignment.
However, while the inspection is repeated, the positions of the needle tips shift by deformation of the probes. When the positions of the needle tips gradually ascend due to deformation of the probes, there may occur the failure of electrical communication between the probes and the electrode pads even when the semiconductor wafer is overdriven. Therefore, Japanese Patent Laid-open Publication No. H5-036765 discloses a prober capable of conducting a stable inspection, wherein a needle trace formed on an actual pad is recognized by a camera to be compared with a reference one, and, if the position of a needle tip ascends, the main chuck is raised to give proper overdrive amounts all the time based on the comparison result.
Japanese Patent Laid-open Publication No. H7-288270 describes an inspection apparatus which obtains position deviation information from a contact state between a virtual pad (design pad) and a probe, so as to virtually monitor a contact state between an actual pad and the probe in advance and correct it to an optimum contact state based on the result from the contact state.
Japanese Patent Laid-open Publication No. 2006-339196 describes a prober, which detects the position of a needle and the position of an electrode, displays an image of a needle trace and a needle trace mark showing the position of the needle trace on a display device, and calculates the positional deviation of the needle trace mark. An operator corrects the position of the needle trace mark on the image, calculates the positional deviation of the needle trace mark, and corrects a movement amount computation corrected value of a semiconductor wafer based on the calculated deviation.
Japanese Patent Laid-open Publication No. 2006-278381 discloses an inspection apparatus wherein, based on the position of needle marks formed on an electrode pad, an amount of deviation of a probe to be contacted subsequently is obtained. Also, in this inspection apparatus, a probe is brought into contact with an electrode pad having thereon an existing needle trace, and then an image after contact which shows a region including the electrode pad is acquired. The image is compared with an image before contact to acquire a newest needle trace, and the amount of positional deviation is corrected using the newest needle trace. The positional deviation amount is then used for the subsequent inspection.
As described above, in all of the conventional techniques, the positional deviation of the electrode pads and the probes can be corrected by acquiring the amount of positional deviation of the electrodes and the probes. However, this correction does not guarantee sure contact between the probes and the electrode pads. Moreover, even though the contact is made, if new needle traces are repeatedly formed on existing needle traces, the electrode pad and the device may be damaged.